Heat storage arrangement

ABSTRACT

A heat storage arrangement for an intermediate storage of thermal energy. The heat storage arrangement includes at least one heat exchanger element which includes a liquid inlet and a liquid outlet, and at least one heat storage container which includes a heat storage medium. The at least one heat exchanger is stiff and has a liquid non-aqueous heat carrier having a freezing point of below −10° C. flow therein. The at least one heat storage container is flexible and closed, and is arranged to abut on the at least one heat exchanger element so that a heat transfer occurs between the liquid non-aqueous heat carrier and the heat storage medium.

CROSS REFERENCE TO PRIOR APPLICATIONS

Priority is claimed to German Patent Application No. DE 10 2016 108 829.3, filed May 12, 2016. The entire disclosure of said application is incorporated by reference herein.

FIELD

The present invention relates to a heat storage arrangement for intermediate storage of thermal energy, and a building heating system comprising a heat storage arrangement.

BACKGROUND

Heat storage arrangements of the above type are known particularly in connection with heat pumps and solar collectors. Of particular advantage hereby are low-temperature heat stores which are usually operated at a temperature of the heat storage medium in the range from 0 to 20° C. The heat store in such an arrangement is connected to a heat pump via a first heat carrier circuit, wherein the heat pump will withdraw heat from the heat store and elevate this heat to a higher temperature level for use in the heating of buildings or the heating of hot water. The heat store is connected to solar connectors via a second heat carrier circuit, which will supply heat to the heat store and thus “charge” the store. On cold days, more heat is withdrawn from the heat store by the heat pump than is supplied by the solar collectors, so that the temperature of the heat storage medium will drop to 0° C. and the heat storage medium will begin to freeze. During the freezing process, as an effect of the phase change of the heat storage medium, latent heat will be released which will be withdrawn from the heat store by the heat pump via the first heat carrier circuit until the heat storage medium has completely frozen. The heat pump can thereby be also operated on cold days when no solar energy is available. The heat store can be “recharged” in that, for example, on sunny days, more heat is supplied to the heat store via the second heat carrier circuit than is withdrawn by the heat pump. Another option for again “recharging” the heat store is by using the heat store for the cooling of buildings. According to this approach, the heat withdrawn from the building will be supplied to the heat store, the heat carrier circulating between the heat store and the building will be cooled down, and the frozen heat storage medium will be melted.

DE 10 2010 037 474 A1 describes a heat storage arrangement comprising a heat storage container which is formed of a firm and of a stiff material and which is completely arranged in the soil. A plurality of tubular heat exchanger elements are arranged in the heat storage container which are surrounded by a heat storage medium contained in the heat storage container and which are connected to different circuits. A first heat exchanger element is connected to a heat pump, and a second heat exchanger element is connected to a heat source, wherein the first heat exchanger element is operative to effect the crystallization of the heat storage medium, and the second heat exchanger element is operative to effect the melting of the heat storage medium.

A disadvantage of the above arrangement is the complex and expensive installation of the heat storage arrangement in the soil because a trench must be excavated for placing the heavy and massive heat storage container therein.

SUMMARY

An aspect of the present invention to provide a further development of a heat storage arrangement for the intermediate storage of thermal energy where the arrangement can be produced and installed in a simple and inexpensive way.

In an embodiment, the present invention provides a heat storage arrangement for an intermediate storage of thermal energy. The heat storage arrangement includes at least one heat exchanger element comprising a liquid inlet and a liquid outlet, and at least one heat storage container comprising a heat storage medium. The at least one heat exchanger is configured to be stiff and to have a liquid non-aqueous heat carrier which has a freezing point of below −10° C. flow therein. The at least one heat storage container is configured to be flexible and closed, and is arranged to abut on the at least one heat exchanger element so that a heat transfer occurs between the liquid non-aqueous heat carrier and the heat storage medium.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:

FIG. 1 schematically shows an embodiment of a heat storage arrangement according the present invention in a lateral view;

FIG. 2 shows a heat exchanger element of the heat storage arrangement according to FIG. 1 in a plan view;

FIG. 3 shows a first building heating system with a heat storage arrangement according to FIG. 1 in a schematic view; and

FIG. 4 shows a second building heating system with a heat storage arrangement according to FIG. 1 in a schematic view.

DETAILED DESCRIPTION

According to the present invention, the heat storage arrangement comprises at least one stiff heat exchanger element and at least one flexible heat storage container, the heat exchanger element being of a plate-shaped design and, by its base face, being in large-surface abutment on an outer surface of the heat storage container.

The heat exchanger element is of a thin-walled design, wherein the thin walls of the heat exchanger element enclose an interior chamber. The heat exchanger element comprises a liquid inlet and a liquid outlet on a first end side so that, via the liquid inlet, a heat carrier will flow into the heat exchanger element and, via the liquid outlet, the heat carrier will flow out of the heat exchanger element. The conductance of the heat carrier within the heat exchanger element is performed via a conduit rib arranged in the interior chamber, the conduit rib extending from the first end side in the direction of an opposite second end side and forming a respective channel between the liquid inlet and the second end side as well as between the liquid outlet and the second end side. The conduit rib comprises an opening at the end of the conduit rib facing toward the second end side via which the two channels are fluidically connected to each other. A U-shaped throughflow is thereby effected through the heat exchanger element, wherein the entire heat exchanger element has the heat carrier flowing through it.

The heat storage container is of a flexible design and comprises an inlet via which the heat storage container can be filled completely with a heat storage medium. The heat storage container is supported by its bottom side on a horizontal surface, for example, the soil, and has a cushion-like shape when completely filled with heat storage medium.

A phase change mass is used as a heat storage medium whose latent heat is considerably larger than its specific heat capacity. Use is thereby made of the enthalpy of the phase change mass in that the heat storage medium, when melting, takes up a great amount of heat and, when solidifying, transmits the heat taken up during melting to the ambience. The excess heat energy which is not needed to heat water on warm days can thereby be used to melt the heat storage medium, and can thereby be stored in the heat storage medium. The heat storage arrangement can further be “recharged” by using the heat storage arrangement for the cooling of buildings. In this case, a heat carrier will circulate between the building and the heat storage arrangement, wherein the heat carrier will take up heat from the building and supply it to the heat storage medium. To allow for a renewed use of the amount of heat stored in the heat storage medium, solidification of the heat storage medium is forced by a continuous withdrawal of heat by causing the heat carrier to flow through the heat exchanger element with a temperature below the solidification temperature of the heat storage medium.

The heat transfer surface formed by the heat exchanger element and the heat storage container is together decisive for the quality of the heat transfer between the heat exchanger element and the heat storage container heat storage container. The heat storage container will adapt to the shape of the heat exchanger element and will provide a large heat transfer surface via the combination of the stiff heat exchanger element, which will not become substantially deformed under high mechanical stresses, and the flexible heat storage container, which will readily become deformed even with small mechanical stresses.

In an embodiment of the present invention, the heat storage medium can, for example, be water. Water is particularly useful as a heat storage medium because the solid-liquid phase change take will take place within a favorable temperature range for the operation of the heat storage arrangement and, in the process, a large amount of heat will be stored and transferred, respectively. Water is also environmentally friendly and inexpensive.

In an embodiment of the present invention, the at least one flexible heat storage container can, for example, be a film bag made of plastic. In the phase change of the heat storage medium from a liquid to a solid state, the volume of some heat storage media, in particular water, will increase due to density anomaly. Under the effect of the increase of volume, the stiff heat storage containers disclosed in the state of the art may be damaged or fully destroyed. The flexible heat storage container, however, because of its deformability, is able to change its shape during the volume increase in the solidification process, whereby the volume within the heat storage container will increase with identical outer circumference and the heat storage container will not be damaged or destroyed.

In an embodiment of the present invention, the at least one flexible heat storage container can, for example, be coated with a heat-ray-reflecting layer, whereby the heat radiation between the ambience and the heat storage container is reduced and, thus, for example, condensation on the outer side of the heat storage container is prevented.

In an embodiment of the present invention, a heat exchanger element carpet can, for example, be provided which is composed of a plurality of stiff heat exchanger elements which, by their base surfaces, are arranged in a single horizontal plane next to each other. In this configuration, the heat exchanger element carpet has the respective base surfaces and top surfaces of the heat exchanger elements arranged in abutment on the bottom side or the top side of the flexible heat storage container, wherein the heat exchanger elements can, for example, be fluidically connected in parallel to each other. Large amounts of heat can thereby be transferred between the heat carrier and the heat storage medium because the heat exchanger element carpet and the heat storage container comprise a large heat transfer surface. The fluidically parallel connection of the individual heat exchanger elements further effects a uniform heat transfer between the heat carrier and the heat storage medium.

In an embodiment of the present invention, at least two heat exchanger elements can, for example, be provided to be fluidically separate from each other, wherein the first heat exchanger element is connectible to a first heat carrier circuit, and the second heat exchanger element is connectible to a second heat carrier circuit. Heat can thereby be withdrawn from the heat storage medium via the first heat carrier circuit and, at the same time, be supplied via the second heat carrier circuit, wherein the first heat carrier circuit is connected to a consumer, and the second heat carrier circuit is connected to a heat source.

In an embodiment of the present invention, at least two separate heat storage containers can, for example, be provided, wherein the stiff heat exchanger element is arranged vertically between the first heat storage container and the second heat storage container. In this configuration, the heat storage elements has its base surface arranged in abutment on the first heat exchanger container and has its top surface arranged in abutment on the second heat exchanger container, resulting in the heat transfer between the heat exchanger element and the two heat storage containers. The quantity of the heat storage medium can thereby be enlarged and the heat storage amount increased. In this embodiment, the upper heat storage container can, for example, have a lower vertical height than the lower heat storage container.

In an embodiment of the present invention, the stiff heat exchanger elements can, for example, be connected to each other via flexible connection elements. It is thereby possible to connect the heat exchanger elements even prior to a final assembly of the heat exchanger arrangement into the heat exchanger element carpet, thereby facilitating the final assembly. The flexible connection of the heat exchanger elements also allows the heat exchanger elements to, for example, be rolled, thereby making transport more convenient and installation easier.

In an embodiment of the present invention, the heat exchanger elements can, for example, comprise reinforcing ribs which, starting from the base surface, extend vertically. By use of the reinforcing ribs, heat exchanger elements can be given a thin-walled design while still enduring high mechanical stresses. High stresses acting vertically to the base surface can in particular be taken up.

In an embodiment of the present invention, a heat insulation trough can, for example, be provided in which the at least one heat exchanger element and the at least one heat storage container are disposed. The heat exchange with the soil is thereby reduced. The heat insulation trough should be made of a thermally well-insulating material.

A heat storage arrangement according the present invention is also provided which together with, for example, a heat pump and solar collectors, allows for a nearly autonomous heat supply of a building.

The heat storage arrangement 10 illustrated in FIG. 1 comprises a first heat storage container 30 and a second heat storage container 40, both of which are realized as a film bag 31, 41 made of plastic and are which arranged in a heat insulation trough 35. Both heat storage containers 30, 40 respectively comprise an inlet 32, 42 via which the heat storage containers 30, 40 are fillable or filled with a heat storage medium 34, usually water. The two heat storage containers 30, 40 differ from each other in their vertical extension, wherein the second (upper) heat storage container 40 has a higher vertical extension than the first (lower) heat storage container 30 by a ratio of 2/3 to 1/3.

A heat exchanger element carpet 21 is arranged vertically between the heat storage containers 30, 40, the heat exchanger element carpet 21 being composed of nine heat exchanger elements 20 arranged in a horizontal plane and fluidically connected to each other via flexible connection elements. The heat exchanger element carpet 21 is, by the base surfaces of the heat exchanger elements 20, in abutment on the first heat storage container 30 and, by the top surfaces of the heat exchanger elements 20, in abutment on the second heat storage container 40. Due to the deformability of the film bags 31, 41, the heat exchanger elements 20 of the heat exchanger element carpet 21 are entirely enclosed in this arrangement by the heat storage containers 30, 40.

FIG. 2 shows a plan view of a heat exchanger element 20. Heat exchanger element 20 comprises a housing 26 made of a stiff plastic material having an inlet 22 and an outlet 24. Via inlet 22, a non-aqueous heat carrier 25, whose freezing point is below −10° C., will flow into the heat exchanger element 20 and will exit from the heat exchanger element 20 via outlet 24. Guidance of the non-aqueous heat carrier 25 in heat exchanger element 20 is performed by the walls of housing 26 and a central conduit rib 23 formed therein. The non-aqueous heat carrier 25 will flow from inlet 22 to an opening 59 arranged opposite to inlet 22 and will flow from there to outlet 24. In addition to central conduit rib 23, the heat exchanger element 20 has reinforcement ribs 52, 54, 56, 58 arranged therein which serve to increase the stiffness of heat exchanger element 20.

FIG. 3 shows a building heating system 60 comprising a solar collector 80, a heat pump 70, and a heat storage arrangement 10. The heat storage arrangement 10 is designed according to the embodiment shown in FIGS. 1 and 2 and comprises a heat exchanger element carpet 21 arranged between the heat storage containers 30, 40. The heat storage containers 30, 40 are only schematically outlined by interrupted lines in FIG. 3. The respective inlets 22 and outlets 24 of the heat exchanger elements 20 are all fluidically connected to a heat carrier circuit 72, wherein the inlets 22 and the outlets 24 are arranged in parallel to each other so that all heat exchanger elements 20 will have the flow passing through them simultaneously.

Heat carrier circuit 72 comprises a first valve 74 and a second valve 76. In a first switching state of valves 74, 76, a non-aqueous heat carrier 25 circulates between the heat exchanger elements 20 and the heat pump 70, the heat being transmitted from the heat storage medium 34 to the non-aqueous heat carrier 25 at a relatively low temperature level and being supplied to the heat pump 70. Heat pump 70 raises the temperature level, thus allowing the heat to be used for the heating of buildings or for the heating of hot water.

In a second switching state of valves 74, 76, non-aqueous heat carrier 25 circulates between a heat exchanger 84 and the heat exchanger elements 20, the circulation being effected by a pump 75. Between heat exchanger 84 and solar collector 80, a heat carrier liquid 89 circulates in a further heat carrier circuit 86, the circulation being effected by a pump 82. In the process, the heat taken up by the heat carrier liquid 89 due to the solar radiation and/or the ambient temperature will be transmitted, in heat exchanger 84, to the non-aqueous heat carrier 25 and be supplied to the heat storage medium 34.

By a regular switching between the two switching states of valves 74, 76, heat can be alternately withdrawn from and supplied to the heat storage medium 34. If no or too little heat is supplied to heat storage medium 34, heat can be withdrawn from the heat storage arrangement 10 by the heat pump 70 until the entire heat storage medium 34 is frozen and no latent heat is available. The heat pump 70 can thereby be used to heat buildings and also to heat hot water on cold days.

FIG. 4 shows a second embodiment of a building heating system 60′ comprising the same components as the first embodiment of the building heating system 60. Different from the first embodiment, the heat storage arrangement 10 comprises a first heat exchanger element carpet 21 and a separate second heat exchanger element carpet 29, both of which are arranged in a common horizontal plane. The first heat exchanger element carpet 21 is connected to a first heat carrier circuit 77, and the second exchanger element carpet 29 is connected to a second heat carrier circuit 79.

The first heat carrier circuit 77 corresponds to the heat carrier circuit 72 of the first embodiment, wherein the first heat carrier circuit 77 comprises a valve 74. In a first switching state of valve 74, the first heat carrier circuit 77 is fluidically connected to heat pump 70 so that the heat pump 70 can withdraw heat from the heat storage medium 34. In a second switching state of valve 74, the non-aqueous heat carrier 25 of the first heat carrier circuit 77 will flow, via heat exchanger 84, back to the heat exchanger elements 20, and will additionally be used to transfer heat between the solar collector 80 and the heat storage arrangement 10.

In the second heat carrier circuit 79, a heat carrier 27 circulates between the heat exchanger 84 and the second heat exchanger element carpet 29, whereby the heat taken up by the solar collectors 80 will be transferred to the heat storage medium 34.

As compared to the described embodiment, other constructional embodiments are also possible which are comprised under the protective scope of the main claim. For example, the heat exchanger elements 20 or the heat storage containers 30, 40 can be designed differently and can, for example, have a different shape. The heating system 60, 60′ can also be designed differently and can, for example, comprise different components so that the heat carrier circuits have a different design. Reference should also be had to the appended claims. 

1. A heat storage arrangement for an intermediate storage of thermal energy, the heat storage arrangement comprising: at least one heat exchanger element comprising a liquid inlet and a liquid outlet, the at least one heat exchanger being configured to be stiff and to have a liquid non-aqueous heat carrier which has a freezing point of below −10° C. flow therein; and at least one heat storage container configured to be flexible and closed, the at least one heat storage container comprising a heat storage medium and being arranged to abut on the at least one heat exchanger element so that a heat transfer occurs between the liquid non-aqueous heat carrier and the heat storage medium.
 2. The heat storage arrangement as recited in claim 1, wherein the heat storage medium is water.
 3. The heat storage arrangement as recited in claim 1, wherein the at least one heat storage container is a film bag made of a plastic.
 4. The heat storage arrangement as recited in claim 1, wherein the at least one heat storage container further comprises a coating of a heat-ray-reflecting layer.
 5. The heat storage arrangement as recited in claim 1, further comprising: a heat exchanger element carpet comprising a plurality of the at least one heat exchanger element, wherein, each of the plurality of the at least one heat exchanger element comprises a respective base surface, the plurality of the at least one heat exchanger element are arranged via their respective base surfaces in a horizontal plane next to each other, and each of the plurality of the at least one heat exchanger element is arranged to abut on the at least one heat storage container.
 6. The heat storage arrangement as recited in claim 5, wherein each of the plurality of the at least one heat exchanger element are fluidically connected in parallel to each other.
 7. The heat storage arrangement as recited in claim 5, further comprising: a first heat carrier circuit; and a second heat carrier circuit, wherein, at least two of the plurality of at least one heat exchanger element are arranged so as to be fluidically separate from each other, a first heat exchanger element is fluidically connectible to the first heat carrier circuit, and a second heat exchanger element is fluidically connectible to the second heat carrier circuit.
 8. The heat storage arrangement as recited in claim 1, wherein, at least two of the at least one heat storage container are separately provided as a first heat storage container and a second heat storage container, and the at least one heat exchanger element is arranged vertically between the first heat storage container and the second heat storage container.
 9. The heat storage arrangement as recited in claim 8, wherein the first heat storage element comprises a vertical height which is lower than a vertical height of the second heat storage element.
 10. The heat storage arrangement as recited in claim 5, further comprising: flexible connection elements, wherein, the plurality of the at least one heat exchanger element are connected to each other via the flexible connection elements.
 11. The heat storage arrangement as recited in claim 5, wherein the at least one heat exchanger element further comprises reinforcing ribs which are configured to extend vertically to the base surface of a respective at least one heat exchanger element.
 12. The heat storage arrangement as recited in claim 1, further comprising: a heat insulation trough configured to have the at least one heat exchanger element and the at least one heat storage container arranged therein.
 13. A building heating system comprising the heat storage arrangement as recited in claim 1, wherein the heat storage arrangement is connected at least to a heat pump. 